Brake cartridges for power equipment

ABSTRACT

Safety systems for power equipment and components and brake cartridges for use in those safety systems are disclosed. The safety systems, components and brake cartridges are specifically applicable for woodworking equipment such as saws. An exemplary brake cartridge includes a housing and a braking component configured to engage a moving part of the power tool upon occurrence of a predetermined event. The brake cartridge may further include a switch configured so that proper installation of the cartridge in the power tool triggers the switch.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional continuation of U.S. patent applicationSer. No. 10/923,273 filed Aug. 20, 2004, and issuing as U.S. Pat. No.7,350,445 on Apr. 1, 2008, which in turn claimed the benefit of andpriority from U.S. Provisional Patent Application Ser. No. 60/496,574,filed Aug. 20, 2003. The disclosures of these applications are herebyincorporated by reference in their entireties.

FIELD

The present invention relates to safety systems for power equipment, andmore particularly, to replaceable brake cartridges for use in safetysystems for woodworking equipment and other power equipment.

BACKGROUND

Safety systems are often employed with power equipment such as tablesaws, miter saws, band saws, jointers, shapers, circular saws and otherwoodworking machinery, to minimize the risk of injury when using theequipment. Probably the most common safety feature is a guard thatphysically blocks an operator from making contact with dangerouscomponents of the equipment, such as blades, belts, or shafts. In manycases, guards effectively reduce the risk of injury, however, there aremany instances where the nature of the operations to be performedprecludes using a guard that completely blocks access to hazardousmachine parts.

Other safety systems try to prevent or minimize injury by detecting andreacting to an event. For instance, U.S. Pat. Nos. 3,953,770, 4,075,961,4,470,046, 4,532,501 and 5,212,621, the disclosures of which areincorporated herein by reference, disclose radio-frequency safetysystems which utilize radio-frequency signals to detect the presence ofa user's hand in a dangerous area of a machine and thereupon prevent orinterrupt operation of the machine. U.S. Pat. Nos. 3,785,230 and4,026,177, the disclosures of which are herein incorporated byreference, disclose a safety system for use on circular saws to stop theblade when a user's hand approaches the blade. The system uses the bladeas an antenna in an electromagnetic proximity detector to detect theapproach of a user's hand prior to actual contact with the blade. Upondetection of a user's hand, the system engages a brake using a standardsolenoid.

U.S. Pat. No. 4,117,752, which is herein incorporated by reference,discloses a braking system for use with a band saw, where the brake istriggered by actual contact between the user's hand and the blade.However, the system described for detecting blade contact does notappear to be functional to accurately and reliably detect contact.Furthermore, the system relies on standard electromagnetic brakesoperating off of line voltage to stop the blade and pulleys of the bandsaw. It is believed that such brakes would take 50ms- Is to stop theblade. Therefore, the system is too slow to stop the blade quicklyenough to avoid serious injury.

The present document discloses safety systems for use on powerequipment. The disclosed safety systems include a replaceable brakecartridge adapted to engage a blade or other cutting tool to protect theuser against serious injury if a dangerous, or triggering, conditionoccurs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of a machine with a fast-actingsafety system.

FIG. 2 is a schematic diagram of an exemplary safety system in thecontext of a machine having a circular blade.

FIG. 3 is a perspective view of a brake cartridge.

FIG. 4 is another perspective view of the brake cartridge shown in FIG.3.

FIG. 5 is a simplified elevation view of a brake cartridge in a tablesaw. Various components of the table saw, including the cabinet, stand,motor, drive belt, etc., have been removed for clarity.

FIG. 6 is shows generally the interior components of the brake cartridgeshown in FIG. 3.

FIG. 7 is a side elevation view of an actuator assembly used in thebrake cartridge of FIG. 3.

FIG. 8 is another side elevation view of the actuator assembly shown inFIG. 7.

FIG. 9 is a front elevation view of the actuator assembly shown in FIG.7.

FIG. 10 is a back elevation view of the actuator assembly shown in FIG.7.

FIG. 11 is a perspective top, front view of the actuator assembly shownin FIG. 7.

FIG. 12 is a perspective bottom, front view of the actuator assemblyshown in FIG. 7.

FIG. 13 is a perspective back, top view of the actuator assembly shownin FIG. 7.

FIG. 14 is a perspective bottom, back view of the actuator assemblyshown in FIG. 7.

FIG. 15 is a top elevation view of the actuator assembly shown in FIG.7.

FIG. 16 is a bottom elevation view of the actuator assembly shown inFIG. 7.

FIG. 17 shows a fuse wire and anchor used in the actuator shown in FIG.7.

FIG. 18 shows a spring housing used in the actuator shown in FIG. 7.

FIG. 19 shows a link used in the actuator shown in FIG. 7.

FIG. 20 shows a lever used in the actuator shown in FIG. 7.

FIG. 21 shows a fulcrum used in the actuator shown in FIG. 7.

FIG. 22 shows a nut used in the actuator shown in FIG. 7.

FIG. 23 is a side elevation view of the actuator shown in FIG. 7 with afuse wire in place holding down a lever pin.

FIG. 24 is a front elevation view of the actuator shown in FIG. 23.

FIG. 25 shows a top view of the actuator shown in FIG. 23.

FIG. 26 shows a cross-section view taken along the line A-A in FIG. 25.

FIG. 27 shows a perspective view of a circuit board used in the brakecartridge shown in FIG. 3.

FIG. 28 shows another view of the circuit board used in the brakecartridge shown in FIG. 3.

FIG. 29 shows a top view of the circuit board shown in FIG. 27.

FIG. 30 shows a bottom view of the circuit board shown in FIG. 27.

FIG. 31 shows the actuator of FIG. 7 with the circuit board of FIG. 28.

FIG. 32 is another view of the actuator of FIG. 7 with the circuit boardof FIG. 28.

FIG. 33 is a side view of the actuator of FIG. 7 with the circuit boardof FIG. 28.

FIG. 34 shows another brake cartridge.

FIG. 35 shows another view of the brake cartridge of FIG. 34.

FIG. 36 is an elevation view of the interior of the brake cartridgeshown in FIG. 34.

FIG. 37 is another elevation view of the interior of the brake cartridgeshown in FIG. 34, with the brake pawl removed for clarity.

FIG. 38 is a perspective view of the brake cartridge shown in FIG. 34with the brake pawl removed for clarity.

FIG. 39 is a perspective view of a fuse wire assembly, with the fusewire bent as it would be when installed in a brake cartridge.

FIG. 40 shows the fuse wire of FIG. 39 without the anchor.

FIG. 41 shows an electrode isolator used in the brake cartridge of FIG.34.

FIG. 42 is another view of the electrode isolator shown in FIG. 41.

FIG. 43 is still another view of the electrode isolator shown in FIG.41.

FIG. 44 is a perspective view of an electrode used in the brakecartridge of FIG. 34.

FIG. 45 is another view of the electrode shown in FIG. 44.

FIG. 46 is an enlarged view of a circuit board and actuator used in thebrake cartridge of FIG. 34, showing the placement of the electrodeisolator.

FIG. 47 shows a lever pin used in the brake cartridge of FIG. 34.

FIG. 48 shows a link used in the brake cartridge of FIG. 34.

FIG. 49 shows a link assembly used in the brake cartridge of FIG. 34.

FIG. 50 shows a side view of the link assembly in FIG. 49.

FIG. 51 shows a top elevation view of the actuator used in the brakecartridge in FIG. 34.

FIG. 52 shows a side elevation view of the actuator in FIG. 51, takenalong the line A-A.

FIG. 53 shows a foam washer that may be used in the brake cartridgeshown in FIG. 34.

FIG. 54 shows an electrode that is used to detect blade-to-pawl spacingin the brake cartridge shown in FIG. 34.

FIG. 55 shows an enlarged side view of a brake cartridge with a switchcontactor and cam bushing.

FIG. 56 shows a perspective view of a switch contactor.

FIG. 57 shows a front elevation view of the switch contactor of FIG. 56.

FIG. 58 shows a side elevation view of the switch contactor of FIG. 56.

FIG. 59 shows a perspective view of a cam bushing.

FIG. 60 shows a front elevation view of the cam bushing of FIG. 59.

FIG. 61 shows a side elevation view of the cam bushing of FIG. 59.

FIG. 62 shows a perspective view of a brake pawl for a dado blade stack.

FIG. 63 shows another perspective view of the brake pawl of FIG. 62.

FIG. 64 shows still another perspective view the brake pawl shown inFIG. 62.

FIG. 65 shows a right side elevation view of a brake cartridge mountedon bracket plates and connected to an arbor block.

FIG. 66 shows a front elevation view of the structure shown in FIG. 65.

FIG. 67 shows a left side elevation view of the structure shown in FIG.65.

FIG. 68 shows a back elevation view of the structure shown in FIG. 65.

FIG. 69 shows a perspective view of a cam bushing.

FIG. 70 shows a front elevation view of the cam bushing in FIG. 69.

FIG. 71 shows a perspective view of a key.

FIG. 72 shows an elevation view of the key in FIG. 71.

FIG. 73 shows two bracket plates.

FIG. 74 is a right side elevation view of the bracket plates in FIG. 73.

FIGS. 75 is a left side elevation view of the bracket plates in FIG. 73.

FIG. 76 is a bottom elevation view of the brake cartridge and otherstructure shown in FIG. 65, with part of the cartridge housing removed.

FIG. 77 shows an arbor link.

FIG. 78 shows another view of the arbor link of FIG. 77.

FIG. 79 shows a perspective view of a plug.

FIG. 80 shows another perspective view of the plug shown in FIG. 79.

FIG. 81 shows a top elevation view of the plug shown in FIG. 81.

FIG. 82 shows half of a cartridge housing isolated from other structure.

DETAILED DESCRIPTION

A machine incorporating a safety system is shown schematically in FIG. 1and indicated generally at 10. Machine 10 may be any of a variety ofdifferent machines adapted for cutting work pieces, such as wood orplastic, including a table saw, miter saw or chop saw, radial arm saw,circular saw, band saw, jointer, planer, etc. Machine 10 includes anoperative structure 12 having a cutting tool 14 and a motor assembly 16adapted to drive the cutting tool. Machine 10 also includes a safetysystem 18, configured to minimize the potential of a serious injury to aperson using the machine. Safety system 18 is adapted to detect theoccurrence of one or more dangerous conditions during use of themachine. If such a dangerous condition is detected, safety system 18 isadapted to engage operative structure 12 to limit any injury to the usercaused by the dangerous condition.

Machine 10 also includes a suitable power source 20 to provide power tooperative structure 12 and safety system 18. Power source 20 may be anexternal power source such as line current, or an internal power sourcesuch as a battery. Alternatively, power source 20 may include acombination of both external and internal power sources. Furthermore,power source 20 may include two or more separate power sources, eachadapted to power different portions of machine 10.

It will be appreciated that operative structure 12 may take any one ofmany different forms. For example, operative structure 12 may include astationary housing configured to support motor assembly 16 in drivingengagement with cutting tool 14. Alternatively, operative structure 12may include one or more transport mechanisms adapted to convey a workpiece toward and/or away from cutting tool 14.

Motor assembly 16 includes at least one motor adapted to drive cuttingtool 14. The motor may be either directly or indirectly coupled to thecutting tool, and may also be adapted to drive work piece transportmechanisms. Cutting tool 14 typically includes one or more blades orother suitable cutting implements that are adapted to cut or removeportions from the workpieces. For example, in table saws, miter saws,circular saws and radial arm saws, cutting tool 14 will typicallyinclude one or more circular rotating blades having a plurality of teethdisposed along the perimetrical edge of the blade. Alternatively, thecutting tool may be a plurality of circular blades, such as a dado bladeor dado stack. For a jointer or planer, the cutting tool typicallyincludes a plurality of radially spaced-apart blades. For a band saw,the cutting tool includes an elongate, circuitous tooth-edged band.

Safety system 18 includes a detection subsystem 22, a reaction subsystem24 and a control subsystem 26. Control subsystem 26 may be adapted toreceive inputs from a variety of sources including detection subsystem22, reaction subsystem 24, operative structure 12 and motor assembly 16.The control subsystem may also include one or more sensors adapted tomonitor selected parameters of machine 10. In addition, controlsubsystem 26 typically includes one or more instruments operable by auser to control the machine. The control subsystem is configured tocontrol machine 10 in response to the inputs it receives.

Detection subsystem 22 is configured to detect one or more dangerous, ortriggering, conditions during use of machine 10. For example, thedetection subsystem may be configured to detect that a portion of theuser's body is dangerously close to, or in contact with, a portion ofcutting tool 14. As another example, the detection subsystem may beconfigured to detect the rapid movement of a workpiece due to kickbackby the cutting tool, as is described in U.S. patent application Ser. No.09/676,190, the disclosure of which is herein incorporated by reference.In some embodiments, detection subsystem 22 may inform control subsystem26 of the dangerous condition, which then activates reaction subsystem24. In other embodiments, the detection subsystem may be adapted toactivate the reaction subsystem directly.

Once activated in response to a dangerous condition, reaction subsystem24 is configured to engage operative structure 12 quickly to preventserious injury to the user. It will be appreciated that the particularaction to be taken by reaction subsystem 24 will vary depending on thetype of machine 10 and/or the dangerous condition that is detected. Forexample, reaction subsystem 24 may be configured to do one or more ofthe following: stop the movement of cutting tool 14, disconnect motorassembly 16 from power source 20, place a barrier between the cuttingtool and the user, or retract the cutting tool from its operatingposition, etc. The reaction subsystem may be configured to take acombination of steps to protect the user from serious injury. Placementof a barrier between the cutting tool and teeth is described in moredetail in U.S. Patent Application Publication No. 2002/0017183 A1,entitled “Cutting Tool Safety System,” the disclosure of which is hereinincorporated by reference. Retracting the cutting tool is described inmore detail in U.S. Patent Application Publication No. 2002/0017181 A1,entitled “Retraction System for Use in Power Equipment,” and U.S. PatentApplication Ser. No. 60/452,159, filed Mar. 5, 2003, entitled“Retraction System and Motor Position for Use With Safety Systems forPower Equipment,” the disclosures of which are herein incorporated byreference.

The configuration of reaction subsystem 24 typically will vary dependingon which action(s) are taken. In the exemplary embodiment depicted inFIG. 1, reaction subsystem 24 is configured to stop the movement ofcutting tool 14 and includes a brake mechanism 28, a biasing mechanism30, a restraining mechanism 32, and a release mechanism 34. Brakemechanism 28 is adapted to engage operative structure 12 under theurging of biasing mechanism 30. During normal operation of machine 10,restraining mechanism 32 holds the brake mechanism out of engagementwith the operative structure. However, upon receipt of an activationsignal by reaction subsystem 24, the brake mechanism is released fromthe restraining mechanism by release mechanism 34, whereupon, the brakemechanism quickly engages at least a portion of the operative structureto bring the cutting tool to a stop.

It will be appreciated by those of skill in the art that the exemplaryembodiment depicted in FIG. 1 and described above may be implemented ina variety of ways depending on the type and configuration of operativestructure 12. Turning attention to FIG. 2, one example of the manypossible implementations of safety system 18 is shown. System 18 isconfigured to engage an operative structure having a circular blade 40mounted on a rotating shaft or arbor 42. Blade 40 includes a pluralityof cutting teeth (not shown) disposed around the outer edge of theblade. As described in more detail below, braking mechanism 28 isadapted to engage the teeth of blade 40 and stop the rotation of theblade. U.S. Patent Application Publication No. 2002/0017175 A1, entitled“Translation Stop For Use In Power Equipment,” the disclosure of whichis herein incorporated by reference, describes other systems forstopping the movement of the cutting tool. U.S. Patent ApplicationPublication No. 2002/0017184 A1, entitled “Table Saw With ImprovedSafety System,” U.S. Patent Application Publication No. 2002/0017179 A1,entitled “Miter Saw With Improved Safety System,” U.S. PatentApplication Publication No. 2002/0059855 A1, entitled “Miter Saw withImproved Safety System,” U.S. Patent Application Publication No.2002/0056350 A1, entitled “Table Saw With Improved Safety System,” U.S.Patent Application Publication No. 2002/0059854 A1, entitled “Miter SawWith Improved Safety System,” U.S. Patent Application Publication No.2002/0056349 A1, entitled “Miter Saw With Improved Safety System,” U.S.Patent Application Publication No. 2002/0056348 A1, entitled “Miter SawWith Improved Safety System,” and U.S. Patent Application PublicationNo. 2002/0066346 A1, entitled “Miter Saw With Improved Safety System,”U.S. Patent Application Publication No. 2003/0015253 A1, entitled“Router With Improved Safety System,” U.S. Patent ApplicationPublication No. 2002/0170400 A1, entitled “Band Saw With Improved SafetySystem,” U.S. Patent Application Publication No. 2003/0019341 A1,entitled “Safety Systems for Band Saws,” U.S. Patent ApplicationPublication No. 2003/0056853 A1, entitled “Router With Improved SafetySystem,” U.S. Provisional Patent Application Ser. No. 60/406,138,entitled “Miter Saw With Improved Safety System,” filed Aug. 27, 2002 bySD3, LLC, and U.S. Provisional Patent Application Ser. No. 60/496,550,entitled “Table Saws with Safety Systems and Blade Retraction,” filedAug. 20, 2003 by SD3, LLC, the disclosures of which are all hereinincorporated by reference, describe safety system 18 in the context ofparticular types of machines.

In the exemplary implementation, detection subsystem 22 is adapted todetect the dangerous condition of the user coming into contact withblade 40. The detection subsystem includes a sensor assembly, such ascontact detection plates 44 and 46, capacitively coupled to blade 40 todetect any contact between the user's body and the blade. Typically, theblade, or some larger portion of cutting tool 14 is electricallyisolated from the remainder of machine 10. Alternatively, detectionsubsystem 22 may include a different sensor assembly configured todetect contact in other ways, such as optically, resistively, etc. Inany event, the detection subsystem is adapted to transmit a signal tocontrol subsystem 26 when contact between the user and the blade isdetected. Various exemplary embodiments and implementations of detectionsubsystem 22 are described in more detail in U.S. Patent ApplicationPublication No. 2002/0017176 A1, entitled “Detection System For PowerEquipment,” U.S. Patent Application Publication No. 2002/0017336 A1,entitled “Apparatus And Method For Detecting Dangerous Conditions InPower Equipment,” U.S. Patent Application Publication No. 2002/0069734A1, entitled “Contact Detection System for Power Equipment,” U.S. PatentApplication Publication No. 2002/0190581 A1, entitled “Apparatus andMethod for Detecting Dangerous Conditions in Power Equipment,” U.S.Patent Application Publication No. 2003/0002942 A1, entitled “DiscreteProximity Detection System,” and U.S. Patent Application Publication No.2003/0090224 A1, entitled “Detection System for Power Equipment,” thedisclosures of which are herein incorporated by reference.

Control subsystem 26 includes one or more instruments 48 that areoperable by a user to control the motion of blade 40. Instruments 48 mayinclude start/stop switches, speed controls, direction controls, etc.Control subsystem 26 also includes a logic controller 50 connected toreceive the user's inputs via instruments 48. Logic controller 50 isalso connected to receive a contact detection signal from detectionsubsystem 22. Further, the logic controller may be configured to receiveinputs from other sources (not shown) such as blade motion sensors, workpiece sensors, etc. In any event, the logic controller is configured tocontrol operative structure 12 in response to the user's inputs throughinstruments 48. However, upon receipt of a contact detection signal fromdetection subsystem 22, the logic controller overrides the controlinputs from the user and activates reaction subsystem 24 to stop themotion of the blade. Various exemplary embodiments and implementationsof control subsystem 26 are described in more detail in U.S. PatentApplication Publication No. 2002/0020262 A1, entitled “Logic Control ForFast Acting Safety System,” U.S. Patent Application Publication No.2002/0017178 A1, entitled “Motion Detecting System For Use In SafetySystem For Power Equipment,” U.S. Patent Application Publication No.2003/0058121 A1, entitled “Logic Control With Test Mode for Fast-ActingSafety System,” and U.S. Provisional Patent Application Ser. No.60/496,568, entitled “Motion Detecting System for use in a Safety Systemfor Power Equipment,” filed on Aug. 20, 2003 by SD3, LLC, thedisclosures of which are all herein incorporated by reference.

In the exemplary implementation, brake mechanism 28 includes a pawl 60mounted adjacent the edge of blade 40 and selectively moveable to engageand grip the teeth of the blade. Pawl 60 may be constructed of anysuitable material adapted to engage and stop the blade. As one example,the pawl may be constructed of a relatively high strength thermoplasticmaterial such as polycarbonate, ultrahigh molecular weight polyethylene(UHMW) or Acrylonitrile Butadiene Styrene (ABS), etc., or a metal suchas aluminum, etc. It will be appreciated that the construction of pawl60 may vary depending on the configuration of blade 40. In any event,the pawl is urged into the blade by a biasing mechanism in the form of aspring 66. In the illustrative embodiment shown in FIG. 2, pawl 60 ispivoted into the teeth of blade 40. It should be understood that slidingor rotary movement of pawl 60 might also be used. The spring is adaptedto urge pawl 60 into the teeth of the blade with sufficient force togrip the blade and quickly bring it to a stop.

The pawl is held away from the edge of the blade by a restrainingmechanism in the form of a fusible member 70. The fusible member isconstructed of a suitable material adapted to restrain the pawl againstthe bias of spring 66, and also adapted to melt under a determinedelectrical current density. Examples of suitable materials for fusiblemember 70 include NiChrome wire, stainless steel wire, etc. The fusiblemember is connected between the pawl and a contact mount 72. Preferably,fusible member 70 holds the pawl relatively close to the edge of theblade to reduce the distance the pawl must travel to engage the blade.Positioning the pawl relatively close to the edge of the blade reducesthe time required for the pawl to engage and stop the blade. Typically,the pawl is held approximately 1/32-inch to ¼-inch from the edge of theblade by fusible member 70; however other pawl-to-blade spacings mayalso be used within the scope of the invention.

Pawl 60 is released from its unactuated, or cocked, position to engageblade 40 by a release mechanism in the form of a firing subsystem 76.The firing subsystem is coupled to contact mount 72, and is configuredto melt fusible member 70 by passing a surge of electrical currentthrough the fusible member. Firing subsystem 76 is coupled to logiccontroller 50 and activated by a signal from the logic controller. Whenthe logic controller receives a contact detection signal from detectionsubsystem 22, the logic controller sends an activation signal to firingsubsystem 76, which melts fusible member 70, thereby releasing the pawlto stop the blade. Various exemplary embodiments and implementations ofreaction subsystem 24 are described in more detail in U.S. PatentApplication Publication No. 2002/0020263 A1, entitled “Firing SubsystemFor Use In A Fast-Acting Safety System,” U.S. Patent ApplicationPublication No. 2002/0020271 A1, entitled “Spring-Biased Brake Mechanismfor Power Equipment,” U.S. Patent Application Publication No.2002/0017180 A1, entitled “Brake Mechanism For Power Equipment,” U.S.Patent Application Publication No. 2002/0059853 A1, entitled “Power SawWith Improved Safety System,” U.S. Patent Application Publication No.2002/0020265 A1, entitled “Translation Stop For Use In Power Equipment,”U.S. Patent Application Publication No. 2003/0005588 A1, entitled“Actuators For Use in Fast-Acting Safety Systems,” and U.S. PatentApplication Publication No. 2003/0020336 A1, entitled “Actuators For UseIn Fast-Acting Safety Systems,” the disclosures of which are hereinincorporated by reference.

It will be appreciated that activation of the brake mechanism willrequire the replacement of one or more portions of safety system 18. Forexample, pawl 60 and fusible member 70 typically must be replaced beforethe safety system is ready to be used again. Thus, it may be desirableto construct one or more portions of safety system 18 in a cartridgethat can be easily replaced. For example, in the exemplaryimplementation depicted in FIG. 2, safety system 18 includes areplaceable cartridge 80 having a housing 82. Pawl 60, spring 66,fusible member 70 and contact mount 72 are all mounted within housing82. Alternatively, other portions of safety system 18 may be mountedwithin the housing. In any event, after the reaction system has beenactivated, the safety system can be reset by replacing cartridge 80. Theportions of safety system 18 not mounted within the cartridge may bereplaced separately or reused as appropriate. Various exemplaryembodiments and implementations of a safety system using a replaceablecartridge, and various brake pawls, are described in more detail in U.S.Patent Application Publication No. 2002/0020261 A1, entitled“Replaceable Brake Mechanism For Power Equipment,” U.S. PatentApplication Publication No. 2002/0017182 A1, entitled “Brake PositioningSystem,” and U.S. Patent Application Publication No. 2003/0140749 A1,entitled “Brake Pawls for Power Equipment,” the disclosures of which areherein incorporated by reference.

While one particular implementation of safety system 18 has beendescribed, it will be appreciated that many variations and modificationsare possible within the scope of the invention. Many such variations andmodifications are described in U.S. Patent Application Publication No.2002/0170399 A1, entitled “Safety Systems for Power Equipment,” U.S.Patent Application Publication No. 2003/0037651, entitled “SafetySystems for Power Equipment,” and U.S. Patent Application PublicationNo. 2003/0131703 A1, entitled “Apparatus and Method for DetectingDangerous Conditions in Power Equipment,” the disclosures of which areherein incorporated by reference.

FIGS. 3 and 4 show a replaceable brake cartridge 100 that may be used inreaction subsystem 24 to stop and/or retract a cutting tool away fromthe point of accidental contact with a user. Brake cartridge 100 isspecifically applicable for use with table saws like those described inU.S. Provisional Patent Application Ser. No. 60/496,550, entitled “TableSaws With Safety Systems and Blade Retraction,” filed on Aug. 20, 2003by SD3, LLC, the disclosure of which is herein incorporated byreference.

FIG. 5 shows a simplified view of a table saw including a table 102 anda blade 104 extending up through the table. The blade is mounted on arotatable arbor 106 that is held in bearings (not shown) mounted in anarbor block 108, as is known in the art. The arbor block is pivotallyconnected by a pin 110 to a rear trunnion 112. The rear trunnion isconnected to a front trunnion 114, and the two trunnions are mounted onfront and rear trunnion blocks 116 and 118, respectively. Manycomponents of the table saw have been removed from FIG. 5 for clarity,including the structure connecting the front and rear trunnions, themotor, the drive belt, the cabinet, the stand, etc. The saw isconstructed so that a user may adjust the elevation and tilt of theblade relative to the tabletop as is known in the art or as is disclosedin the references incorporated herein by reference.

FIG. 5 shows cartridge 100 mounted in the table saw on pin 110. Thecartridge is held in place by a bracket 120 supported by pin 110 andconnected to arbor block 108. As can be seen in FIG. 5, brake cartridge100 is positioned close to the perimeter of blade 104 so that if thedetection subsystem in the saw detects a dangerous condition, the brakecartridge can react quickly to engage and stop the blade. The cartridgeand bracket are configured so that the position of the cartridgerelative to the blade is maintained when the blade elevation or tiltchanges. For example, the bracket and cartridge are supported by pin 110so that the bracket and cartridge can pivot up or down when the arborblock and blade pivot up or down.

As shown in FIGS. 3 and 4, cartridge 100 includes a housing 122. Thehousing is typically made from a molded thermoplastic, such as ABS orPCABS, and it encloses various components, as explained below. Housing122 is made of two halves 124 and 126, and the halves are joinedtogether by screws and nuts as shown. Alternatively, the halves may bejoined by an adhesive, sonic welding, snap fits, etc., or a combinationof these methods. It is desirable that the housing be sealed so thatdust or other debris does not enter the cartridge and impair thefunctioning of the various components therein.

Cartridge 100 includes an end 128 defining an annular opening that isconfigured to slide over a pin to mount the cartridge in a saw, such aspin 110 shown in FIG. 5. The cartridge also includes a tab 130 (shown inFIGS. 3, 4 and 6) configured to slide over a flange on bracket 120 tohelp hold the cartridge in place in the saw.

Brake cartridge 100 also includes a brake pawl 132 designed to engageand stop a spinning blade. Specifically, the pawl is designed to pivotout into contact with the teeth of a spinning blade so that the teethcut into the pawl and bind, thereby stopping the blade from spinning.Pawl 132 is formed from fully annealed aluminum, which is sufficientlysoft for the teeth of a spinning blade to cut into while also beingsufficiently strong to stop the blade. However, as stated above, thepawl may be made from a number of materials. It has been found thatpawls made from fully annealed aluminum stop the blade significantlyfaster than pawls made from other materials such as thermoplastic. Forexample, a pawl made from a thermoplastic such as ABS may stop a 10inch, 28 tooth blade spinning at approximately 3500 rpms inapproximately 5 milliseconds, while a pawl made from fully annealedaluminum may stop the same blade in approximately 2 to 3 milliseconds orless. It has also been learned that pawls made of fully annealedaluminum work significantly better in stopping 200 tooth blades andplywood blades than pawls made from thermoplastic because the aluminumis less likely to collect in the gullets between the teeth of the blade.

Brake pawl 132 includes an annular aperture 134 that is sized to fitover the outside of end 128, as shown in FIGS. 3 and 4. In this manner,brake pawl 132 may pivot around end 128. The brake pawl and housing areassembled by inserting end 128 of one half of housing 122 into aperture134, inserting end 128 of the other half of housing 122 into theaperture, and then joining the two halves together.

End 128 includes a slot 133 that extends completely through the end fromone side of the housing to the other. Slot 133 functions to prevent pawl132 from binding on end 128. If debris collects between end 128 and pawl132, or if heat causes end 128 to expand more than the pawl expands sothat the brake pawl binds on end 128, then as brake pawl pivots out oraway from housing 122, end 128 will compress because of the slot andthereby release the pawl. Thus, slot 133 helps insure that pawl 132 isalways able to pivot out into contact with the blade. End 128 also mayhave a recessed section on its outer surface to minimize any frictionbetween end 128 and pawl 132.

Pawl 132 includes a curved surface 136 configured to match the curvatureof the perimeter of a blade. Thus, when the pawl pivots out into contactwith the blade, the entire surface will contact the blade at the sametime and stop the blade quicker than if only part of the surfacecontacted the blade.

A plurality of holes, such as hole 138, are cut into pawl 132immediately below surface 136. These holes create what may be thought ofas a collapse zone. The holes make it easier for the teeth of a spinningblade to cut into the pawl and bind.

Pawl 132 also includes several large holes, such as hole 140. Theseholes minimize the mass of the pawl so that with a given force the pawlcan accelerate into the blade faster. The large holes also createanother collapse zone so that the pawl can deform to absorb the energyof the spinning blade. It is desirable for the pawl to absorb the energyof the blade by deforming because otherwise stopping the blade may bendor damage the arbor on which the blade is mounted.

Pawl 132 may take different shapes for different blades. The pawl shownin FIGS. 3 and 4 is designed for blades with 10 inch diameters. The pawlmay be wider and longer for 7 or 8 inch dado blades, for example. FIGS.62 through 64 show a pawl 133 designed for an 8 inch dado stack up to13/16ths of an inch wide. The pawl is designed to be mounted on acartridge housing like housing 122 discussed above. The pawl is thickerand longer so that it is adjacent the perimeter of the dado stack whenthe cartridge is installed in the saw.

FIG. 6 shows brake cartridge 100 with one half of the housing removed sothat internal components are visible. These components include anactuator assembly 150 and electronics 152.

Actuator assembly 150 is the portion of cartridge 100 that causes pawl132 to move into the blade upon the detection of a dangerous condition.The actuator assembly includes a coil spring held in compression by alever pin on a fulcrum. A link extends up through the coil of the springand over one end of the lever, and a fuse wire is looped over the otherend of the lever. When a dangerous condition is detected, a surge ofelectricity burns the fuse wire, releasing the lever pin. The springthen expands, pushing the pawl out, into the teeth of the spinningblade.

Actuator assembly 150, and the individual components that make up theassembly, are shown in more detail in FIGS. 7 through 26. The actuatorassembly is shown in cross-section in FIG. 26. The assembly includes acoil spring 152 (shown in FIG. 26) that exerts approximately 150 poundsof force when compressed. Of course, various springs that exertdifferent forces can be used. Generally, the greater the force thefaster the actuator, but the more difficult it is to hold the spring incompression and release the spring quickly.

Compressed spring 152 is housed in a spring housing 154 shownindividually in FIG. 18. The spring housing is a generally cylindricalhousing with an interior cavity shaped and sized to accommodate spring152 and hold the spring stable when compressed. An annular flange 156 isrecessed slightly from the top of the spring housing, with the flangeextending inwardly around the inside of the housing, leaving a hole 158.The annular flange defines the bottom of a recess in which is placed acap 160 (shown individually in FIG. 21). Cap 160 is stamped from sheetmetal, and it includes a flat edge 162. The recess in the spring housingincludes a corresponding flat edge so that the cap can be placed in therecess in one orientation only. Cap 160 also includes a fulcrum 164having a notch 166. A lever pin 170 (shown individually in FIG. 20),made from hardened steel, such as ⅛-inch-diameter music wire, includes anotch 172, and the lever pin is positioned on fulcrum 164 so that notch166 in the fulcrum and notch 172 in the lever pin mesh. Notch 166 in thefulcrum is “V” shaped so that the lever pin will nest into notch 166.

A link 174 (shown individually in FIG. 19) includes a hardened steelwire 176 that is curved to form an inverted “U” shape. The ends of thewire are insert molded into a base 178, and the ends may be kinked orbent to minimize the possibility of the wire pulling out of the base.The wire loop may be made of music wire, and should have a tensilestrength sufficient to hold the coil spring in compression over time.Base 178 also may be referred to as a yoke because it spans across aportion of brake pawl 132, as shown in FIGS. 3, 4 and 6. The yokeincludes four holes, like hole 180 shown in FIGS. 12, 14 and 19. Brakepawl 132 includes corresponding holes. Pins or screws are insertedthrough the holes to join the yoke to the brake pawl. The bottom of theyoke also includes a ridge 182 to strengthen the yoke, and the surfaceof the brake pawl over which the yoke spans is shaped to accommodate theridge.

Link 174 is inserted up through coil spring 152 and over the end oflever pin 170, as shown in FIG. 26. Lever pin 170 includes a secondnotch 184 over which link 174 extends, and the end of lever pin 170between notches 172 and 184 tapers down to a size corresponding to thebend in wire 176. Notch 184 is sized and configured so that link 174 maycome off the lever pin cleanly when the lever pin is released, asexplained below.

Link 174 also includes a raised central portion 186 that helps positionthe spring relative to the link and helps hold the spring stable when itis compressed, as shown in FIG. 26. The raised central portion is sizedand configured to correspond to the inner dimensions of coil spring 152.Raised central portion 186 includes a tapered surface 188 that makes iteasier to insert the raised central portion into the coil spring.

Base 178 of the link includes a slightly raised, circular section 190with a tapered edge 192. Section 190 is configured to correspond to thebase of spring housing 154, as shown in FIG. 26. Tapered edge 192 isconfigured to mesh with the bottom edge of a nut 194, also shown in FIG.26. The nut is shown individually in FIG. 22, and it includes internalscrew threads 196. The bottom of spring housing 154 includescorresponding, external screw threads 198.

When assembled, nut 194 is threaded onto spring housing 154, and link174 is held against the bottom of the spring housing by the lever pin.The nut may then be threaded down until it presses against base 178 oflink 174, as shown in FIG. 26. Nut 194 includes a knurled edge 200 sothat the nut can be turned by hand. The nut is threaded down against thebase of the link in order to seal the actuator against the entry of dustor other contaminants. A foam washer (not shown) may be inserted andcompressed between nut 194 and base 178 to further effectuate a seal.Nut 194 also is threaded down against base 178 to help hold thecompressed spring stable and to take up any play in the linkage betweenthe lever, spring, spring housing, cap, and link resulting frommanufacturing tolerances.

A fuse wire assembly 210 is shown in FIG. 17, including an inverted “U”shaped wire 212 insert molded into an anchor 214. Wire 212 is a hardenedsteel wire such as music wire, and the ends of the wire may be kinked orbent to minimize the possibility of the wire pulling out of the anchor.Anchor 214 is shaped to fit into a socket 216 in spring housing 154, andthe anchor includes shoulders 218 to help hold the anchor in the socket.

When the fuse wire assembly is initially placed into socket 216, wire212 extends up and around lever pin 170, as shown in FIGS. 7 through 14.During assembly of the actuator, wire 212 is twisted above the lever pinand then pulled down over the lever pin and around shoulders 220 inspring housing 154, as shown in FIGS. 23 through 26. (FIGS. 39 and 40also show how the wire is twisted in the context of an alternative fusewire assembly.) Twisting wire 212 and pulling it down so that it extendsaround shoulders 220 causes four strands of the wire to hold down thelever pin. Lever pin 170 includes notches 222 and 224 over which thefuse wire extends.

When assembled, actuator 150 holds spring 152 in compression by link 174and fuse wire assembly 210 holding lever pin 170 on fulcrum 164. Spring152 and link 174 exert a force tending to pull the lever pin down, butthe lever pin is held in place by the fuse wire. The fuse wire ispositioned over the lever pin a sufficient distance from fulcrum 166 inorder to provide a mechanical advantage to help hold the lever pin inplace. The mechanical advantage allows the fuse wire to be smaller andless strong that it otherwise would have to be. In actuator 150, themechanical advantage is approximately 3:1. Thus, notches 222 and 224 areapproximately three times further from notch 172 than notch 184 is fromnotch 172. With a 3:1 mechanical advantage and a spring that exerts a150-pound force when compressed, the fuse wire would need to holdapproximately 50 pounds of force. However, because the fuse wire istwisted so that four strands of the wire together hold the lever down,each strand of wire would need to hold approximately 12 to 13 pounds offorce. Music wire of approximately 0.010-inch diameter is believed tohave sufficient tensile strength to hold that force. It is advantageousto use a fuse wire with a relatively small diameter because the fusewire must be fused in order to release the spring and smaller diameterwires are easier to fuse. The mechanical advantage discussed aboveallows for a small diameter fuse wire to hold a large force.

Actuator 150 is assembled using a jig that holds the spring incompression while lever pin 170, link 174 and fuse wire 210 arepositioned. Shoulders 220 on spring housing 154 may include a taperededge 226 (labeled in FIGS. 12 and 18) to make it easier to slide thefuse wire onto the shoulders during assembly. The shoulders themselvesmay be slightly sloped to keep the fuse wire from sliding off theshoulders. The jig is then released, and the spring puts tension on thelink and fuse wire to hold the assembly together. When assembled,actuator 150 is quite stable because spring 152 exerts a significantforce on lever pin 170 and because the compressed spring is enclosed inhousing 154.

Spring housing 154 also includes a raised flange 228 positioned adjacentthe end of lever pin 170, as shown in FIGS. 18, 23 and 26. Raised flange228 functions to prevent lever pin 170 from being improperly positionedduring assembly. Specifically, flange 228 prevents lever pin 170 frombeing positioned so that it is balanced on fulcrum 164 between notch 172and notch 184.

Housing 154, link base 178, and fuse wire anchor 214 are typically madefrom a moldable material that has very little creep, or in other words,is very dimensionally stable over time. It is important that thematerial be able to maintain its shape and withstand the constant forceof the compressed spring on the link and fuse wire. Otherwise, forexample, if the shape of shoulders 220 changed, then the fuse wire couldbecome sufficiently slack so that link 174 could slip off the lever pinand accidentally release the spring. The material must also besufficiently strong so that the fuse wire does not pull out of anchor214, and so the link wire does not pull out of base 178. The materialmust also have little moisture absorption and little heat expansion sothat the molded parts maintain their shapes and dimensions in varioushumid, dry, hot or cold climates. In the shown embodiment, housing 154,link base 178 and fuse wire anchor 214 are molded from a phenolic,thermoset material having very little creep. One such material is RX630from a company called Vyncolit.

In the embodiment shown, fuse wire assembly 210 is separate from springhousing 154 to facilitate manufacturing. It is important that the lengthof fuse wire extending out from fuse wire anchor 214 be quite precise,otherwise there could be slack in the fuse wire allowing the link toslip off the lever pin. It is easier to make the fuse wire precise ifthe wire is insert-molded in a separate part. It is also easier toinsert the fuse wire into a simple mold such as would be required forthe fuse wire anchor. It would be difficult to insert the fuse wire intothe mold for the spring housing. Nevertheless, the fuse wire could beinsert-molded into the spring housing directly to eliminate the separatefuse wire anchor assembly.

It is also important that the length of link wire 176 extending out fromlink base 178 be sufficiently precise to prevent the link or fuse wirefrom slipping free.

Both the fuse and link wires must be sufficiently strong to withstandthe tensile loads place on them, respectively. They must also be able tobend into the necessary shapes without breaking.

Cap 160 and lever pin 170 must be made of materials sufficiently strongto withstand the loads placed thereon. As stated, cap 160 may be stampedfrom sheet metal, and lever pin 170 may be machined from hardened steelsuch as ⅛-inch diameter music wire, for example.

Nut 194 may be molded from many materials, such as a thermoplastic likeABS.

When assembled, actuator 150 provides a compact, stable unit. Theactuator is cocked and ready to apply a significant force when the fusewire is severed, as will be explained below. The actuator may remain inits cocked condition for a significant period of time. The actuator isself-contained so that it may be easily placed into brake cartridge 100.While actuator 150 is described in the context of a brake cartridge usedin a safety system for power equipment, it is believed that actuator 150is a significant improvement in many respects over other actuators, andthat there are many other possible uses of actuator 150.

FIGS. 27 through 30 show electronics 152 used with actuator 150 in brakecartridge 100. Electronics 152 include a printed circuit board 240 onwhich is mounted various electronic components used in the reactionsubsystem described above, including capacitor 242. Other components onthe circuit board may be those required for a firing circuit, asdescribed above and as described in the references incorporated byreference.

Circuit board 240 also includes a card edge plug 244 on which would betraces for connecting the electronics to the rest of the saw via a cardedge connector. Card edge plug 244 is also shown in FIG. 4 extending outfrom housing 122 of the brake cartridge. The cartridge is electronicallyconnected to other components in the saw by plugging card edge plug 244into a card edge connector mounted in the saw on bracket 120. Cartridge100 may be sealed around card edge plug 244 by having the card edgeextend out of the housing through a piece of foam on the inside wall ofthe housing, and by having the slot in the housing through which thecard edge plug extends be only slightly larger than the card edge plugitself. Of course, various types of plugs may be used in place of a cardedge connector.

Circuit board 240 includes an end 245 shaped to fit into a socket 248 inspring housing 154. (Socket 248 is labeled in FIGS. 18, 24 and 26.)Socket 248 is configured and positioned relative to shoulders 240 sothat fuse wire 212 spans across the bottom of the socket when the fusewire is placed around shoulders 240. FIGS. 31 through 33 show how end245 fits into socket 248. Fuse wire 212 is not shown in FIGS. 31 and 33in order to show clearly how end 245 fits into the socket. (A fuse wireextending across electrodes is shown in FIG. 46.)

Two electrodes 250 and 252 are mounted on circuit board 240 on the sideopposite the capacitor. The electrodes are typically formed wires. Theelectrodes are fitted into the circuit board and electrically connectedto the capacitor via conductive traces. When end 245 of circuit board240 is plugged into socket 248, electrodes 250 and 252 are in the bottomof the socket, as shown in FIG. 32. Fuse wire 212 would then extend overand across the two electrodes so that the fuse wire touches and bridgesthe electrodes. Socket 248 is configured relative to shoulders 240 onthe spring housing, so that when end 245 of the circuit board isinserted into the socket, electrodes 250 and 252 press against the fusewire. Socket 248 may include sloped or shaped surfaces to direct,position and hold end 245 properly in the socket. In this manner,actuator 150 is operatively coupled to electronics 152.

The coupled actuator 150 and electronics 152 may then be dropped intothe housing of the brake cartridge. The housing typically would includeinternal ribs and flanges to position and hold the actuator andelectronics in place.

In use, when the detection subsystem detects a dangerous condition, asignal is sent to electronics 152 in the brake cartridge causingcapacitor 242 to discharge to ground by passing current from oneelectrode to the other through fuse wire 212. The size of the capacitoris chosen so that the current density discharged to ground issufficiently high to fuse or break the fuse wire. When the fuse wirebreaks, lever pin 170 is freed and spring 152 is released. The springquickly expands, pushing pawl 132 out into the teeth of the blade.

The configuration of the fuse wire and electrodes as described aboveallows one break of the fuse wire to release all four strands of thewire holding down the lever pin. The fuse wire then unwraps from overthe lever pin as the spring expands. The manner in which the fuse wireis twisted over the lever pin, and the way the fuse wire extends overshoulders 220 on the spring housing, allows the fuse wire to unwrapcleanly without tangling.

When the fuse wire breaks, lever pin 170 pivots down around fulcrum 164.As shown in FIG. 6, cartridge housing 122 includes a dome-shaped section254 positioned adjacent lever pin 170 so that the lever pin is free topivot around fulcrum 164 without catching.

Spring 152 will expand quickly when fuse wire 212 breaks. Flange 156 andcap 160 provide a surface against which the spring presses when itexpands. Housing 122 typically would include ribs and/or flanges tosupport and securely hold the spring housing in place. Housing 122 alsoincludes a tab 130, as discussed above, which helps secure and hold thebrake cartridge in the saw. Housing 122 includes ribs, such as ribs 256shown in FIGS. 3 and 4, to strengthen tab 130 so that it can withstandthe force of the spring and transfer the force to the bracket holdingthe cartridge. Using flanges and ribs to strengthen tab 130, andsecurely mounting the cartridge to bracket 120 by tab 130, ensures thatspring 152 pushes brake pawl 132 out instead of pushing the cartridgeback.

Actuator 150 is capable of applying a significant force very quickly. Inthe embodiment shown, actuator 50 can supply 150 pounds of forceinstantly after the fuse wire is fused. This is significant because thequicker actuator 50 can apply the force to move the brake pawl into thespinning blade, the quicker the blade will stop, minimizing any injury.

Brake cartridge 100 is designed for installation in a right-tilt saw. Inother words, the cartridge is designed for a saw where the blade abovethe table tilts to the right relative to a user standing in front of thesaw. The cartridge could be mirrored for a left-tilt saw.

Another brake cartridge is shown in FIGS. 34 and 35 at 300. Much ofcartridge 300 is similar to previously described brake cartridge 100.For example, brake cartridge 300 includes a housing 302 and a brake pawl304 joined as described above in connection with cartridge 100.Additionally, housing 302 typically would include a tab like tab 130shown in FIGS. 3 and 4, but the tab is not shown in connection withcartridge 300. Cartridge 300 also includes a D-sub plug 303 that may beused instead of the card edge plug described above. Cartridge 300 isalso designed for a left-tilt saw instead of a right-tilt saw. Otherdifferences between the two cartridges are discussed below.

The interior of brake cartridge 300 is shown in FIGS. 36 through 38,including an actuator 306. The actuator is shown positioned in thecartridge similarly to actuator 150 described above. Ribs, such as ribs308, are shown in the housing to support the actuator and to providestrength to the housing, as discussed above.

FIG. 39 shows a fuse wire assembly 310 used in actuator 306. Fuse wireassembly 310 includes a fuse wire 312 insert-molded into an anchor 314.Fuse wire 312 is shown twisted and down, as if it were wrapped over thelever pin and around the shoulders on the spring housing. FIG. 40 showsfuse wire 312 without anchor 314 so that the ends of the wire arevisible. Each end of the fuse wire includes bends 316 that help preventthe wire from pulling out of the anchor.

Fuse wire 312 is configured to extend over two electrodes on a circuitboard so that a surge of electricity can be sent from one electrode tothe other through the fuse wire to break the wire, as described above.An electrode used in actuator 306 is shown at 318 in FIGS. 44 and 45.Electrode 318 is a “U” shaped piece of wire with two ends 320 5 and 322that are soldered onto the circuit board. A section 324 extends betweenends 320 and 322.

It is important that the fuse wire contact both electrodes. However, ifone electrode is soldered on the circuit board higher than the other,then the fuse wire may touch only one electrode. Also, because theelectrodes are positioned close to each other on the circuit board, itis also conceivable that the fuse wires may touch or become electricallyconnected and allow current to pass from one to the other withoutbreaking the fuse wire. Brake cartridge 300 includes a fuse wireisolator to address these issues. A fuse wire isolator 320 is shown inFIGS. 41 through 43.

Fuse wire isolator 320 is a small molded part having two channels 322and 324. 15 The channels terminate in holes 326. The electrodes fit intothe channels, and the ends of the electrodes extend through the holes tothe circuit board. The channels are configured with sloping sidesurfaces so that the electrodes are directed into predeterminedpositions when the electrodes are inserted into the channels. Twosloping surfaces are shown at 328 and 330 in FIG. 43. The slopingsurfaces create a slight bend in the electrodes, as 20 shown at 332 inFIG. 45. The electrodes may be pre-bent to fit into the channels, or thechannels themselves may cause the electrodes to bend. Also, each ofholes 326 have one side that is vertical relative to the bottom of theelectrode isolator, and another side that is sloped so that the holesare somewhat cone shaped. The somewhat conical-shaped holes make iteasier to insert the electrodes into the holes, and help to direct theelectrodes into the proper position, while the narrower terminus of eachhole tends to hold the electrode in place. Channels 322 and 324 are alsooffset from each other, as shown in FIG. 43. When the electrodes aresoldered onto the circuit board, the solder will typically extendoutward from the electrodes. If the electrodes are positioned tooclosely, then the solder surrounding one electrode may touch andelectrically connect to the solder surrounding another electrode, whichcould prevent the electrodes from passing current through the fuse wire.Offsetting the electrodes as shown in FIG. 43 permits the electrodes tobe positioned closer together than they otherwise could be because thesolder pads will be offset.

The fuse wire isolator also includes a slot 334 extending transverselyacross channels 322 and 324. Fuse wire 312 fits into slot 334, and slot334 directs the fuse wire across the electrodes. The fuse wire isolator,including slot 334, is shaped to hold the electrodes in positions wherethe fuse wire must contact and extend over both electrodes. The fusewire isolator may be thought of as creating a path over the electrodesfor the fuse wire to follow.

FIG. 46 shows fuse wire isolator 320 mounted on the bottom of a circuitboard with fuse wire 312 extending across the electrodes. Severalcomponents from actuator 306 have been removed to show the fuse wireisolator clearly.

FIG. 47 shows a lever pin 340 used in actuator 306. Lever pin 340includes a notch 342 for the fulcrum, notches 344 and 346 for the fusewire, and notch 348 for the link assembly. Notch 348 in lever pin 340 ismore rounded than corresponding notch 184 in lever pin 170 shown in FIG.20. The more rounded notch accommodates the alternative link assemblydiscussed below.

FIGS. 49 and 50 show a link assembly 350 used in actuator 306. Linkassembly 350 includes a link 352 insert molded into a base 351. Link 352is a thin, stamped metal part, and is shown isolated in FIG. 48. Thematerial from which the link is made should be sufficiently strong towithstand the tension and force of the spring when the actuator isassembled. One possible material is 20% cold worked steel or stainlesssteel. The link includes an aperture 354 that fits over notch 348 on thelever pin. Using a stamped metal link 352 instead of a link wire avoidsthe issue of bending the wire into an inverted “U” shape, which mayweaken or even crack the wire at the bend. Link 352 also includes holes356 that are buried in base 351 during molding. The material forming thebase flows into holes 356 during molding; thereby minimizing the chancethat link 352 will pull out of the base. Base 351 includes holes 358through which pins or screws are inserted to join the base to the brakepawl, as described above. Holes 358 are somewhat oval shaped to allowfor some lateral movement of the base relative to the brake pawl.Lateral movement may result from plastic or thermoset parts such as base351 expanding or contracting at rates different from the aluminum brakepawl.

FIG. 51 shows a top view of actuator 306. Lever pin 340 is balanced on afulcrum with link 352 over one end of the lever and fuse wire 312 overthe other end of the link. FIG. 52 is a cross-section side view ofassembled actuator 306 taken along the line A-A in FIG. 51. FIG. 52shows how the various components fit and work together to form theactuator.

FIG. 53 shows a foam washer 360 that may be placed around the capacitorin the cartridge. The foam washer shields the capacitor and dampens anyvibrations that may adversely affect the capacitor.

FIG. 54 shows an electrode 362 used in brake cartridge 300 to detectwhether the spacing between the blade and brake pawl is appropriate. Ifthe spacing is too great, then a more severe injury could result becauseit would take longer to move the brake pawl into the blade to stop theblade. Also, a user may install a blade in the saw for which the brakecartridge is not designed. For example, a user may inadvertently installan 8-inch blade in a saw that has a brake cartridge designed for a10-inch blade. In that case, the brake pawl may not be able to reach theblade if an accident occurs. Checking the blade-to-pawl spacing, andallowing the saw to function only if the spacing is within acceptablelimits, addresses these issues.

FIGS. 37 and 38 show electrode 362 mounted in cartridge 300. Electrode362 includes two tabs 364 that are soldered onto the circuit board usedin the cartridge. A portion 366 extends up and away from tabs 364 and isdimensioned so that it can pass through slot 367 in the housing, asshown in FIGS. 37 and 38. Slot 367 may include flanges extending intothe cartridge to create a slot longer than the wall thickness of thecartridge housing (as shown in FIG. 55). A longer slot provides a betterdust seal around portion 366. The housing of the cartridge includes anoutwardly extending flange 365 that extends around electrode 362 toprotect the electrode and to provide more of a labyrinth seal to preventdust from entering the cartridge through slot 367.

The end of the electrode opposite portion 366 includes a folded tab 368that fits into socket 370 in the housing. A section 370 of the electrodeextends between portion 366 and tab 368 outside of the cartridge andbetween the housing and the brake pawl, as shown. Section 370 isslightly arched to insure it touches the brake pawl when the brake pawland housing are joined. Section 370 also includes raised tabs 372 thatextend up to contact the brake pawl. When the brake pawl and housing arejoined, the tabs will contact the pawl and scrap along the pawl as thepawl pushes the tabs and section 370 down toward the housing, therebyhelping to ensure contact between the electrode and the pawl.

To assemble the cartridge, electrode 362 is soldered to the circuitboard and then the entire circuit board and actuator are placed in onehalf of the cartridge housing by sliding the electrode into slot 367 andsocket 370. The other half of the cartridge then closes socket 370 andslot 367, trapping the electrode in place.

Electrode 362 electrically connects the brake pawl to the electronics inthe brake cartridge. That connection, in turn, permits the brake pawl toact as a sensor to detect whether the blade is within a specifieddistance. As explained above, and as explained in the documentsincorporated by reference, an electrical signal is placed on the bladeand used by the detection subsystem to detect when a person contacts theblade. That same signal will induce a corresponding signal on the brakepawl because the perimeter of the blade and the surface of the brakepawl will create a capacitive coupling. In other words, the signal onthe blade will capacitively induce a signal on the brake pawl. Thesignal on the brake pawl can then be measured to determine whether theblade is sufficiently close to the pawl. Additional information aboutdetecting blade-to-pawl spacing is set forth in the documentsincorporated by reference.

FIG. 55 shows a small tactile switch 380 mounted on circuit board 240 inbrake cartridge 300. The switch includes a button 382 that is pressedand released to toggle the switch. Switch 380 is used to signal thecontrol subsystem that the brake cartridge is fully installed in thesaw. If the cartridge is not fully installed in the saw, the saw willnot run.

A switch contactor 384 is positioned adjacent switch and is designed tomove up and down, into and out of contact with button 382. Switchcontactor 384 is made from a thin piece of sheet metal, and is shownisolated in FIGS. 56 through 58. The switch contactor includes a foldedtab 386, as shown. Tab 386 is the part of the switch contactor thatactually contacts button 382. Tab 386 is folded to help insure contactis made with button 382, and also to apply a somewhat predetermined andcontrolled force to the button. The tab will flex when it contactsbutton 382 and will prevent too much force from being applied to button382. When flexed, the tab will also urge the spring contactor away frombutton 382.

Switch contactor 384 is mounted on a cam bushing 388. Cam bushing 388 isa somewhat cylindrical part, shown isolated in FIGS. 59 through 61. Cambushing 388 includes an annular outer flange 390, and an annularsnap-ring 392 distal from flange 390. The cam bushing is mounted in abore in the housing of the brake cartridge, as shown in FIGS. 34 and 35.The bore in the housing is shown in FIG. 82. The cam bushing is pushedinto the bore until flange 390 abuts the outer surface of the housingand snap-ring flange 392 snaps over a corresponding shoulder in thebore. When installed, the cam bushing may rotate in the bore around itslongitudinal axis.

The cam bushing includes an end 394 that extends into the brakecartridge and on which switch contactor 384 is mounted. Switch contactor384 includes an aperture 396 that fits over end 394 of the cam bushing.The periphery of aperture 396 includes cam surfaces 398 and 400. Aflange 402 on end 394 of the cam bushing is designed to contact the camsurfaces.

When cam bushing 388 rotates counterclockwise, as seen in FIG. 55,flange 402 will rotate without causing the spring contactor to moveuntil flange 402 contacts cam surface 398. As flange 402 contacts camsurface 398 and continues to rotate, flange 402 will slide over the camsurface and cause the switch contactor to move into contact with switch380. Switch contactor 384 includes apertures 404 (labeled in FIGS. 56and 57), which are shaped to fit around pins 406 in the housing. Theapertures are oval shaped so that the switch contactor may move up anddown, into and out of contact with switch 380, but not side-to-side.Apertures 404 and pins 406 are positioned around the switch contactor tosupport the contactor as it moves. The switch contactor is held on thepins, and on cam bushing 388, by the other half of the cartridgehousing. When cam bushing 388 rotates clockwise, as seen in FIG. 55,flange 402 will contact and slide along cam surface 400, causing switchcontactor 384 to move out of contact with switch 380. In this manner,the switch contactor and cam bushing provide a simple mechanism toconvert the rotary movement of the cam bushing into translational motionof the switch contactor. A stop may be incorporated on the cam bushingto limit the distance the bushing rotates.

Cam bushing 388 includes a central bore 410. It is intended that cambushing 388 be rotated with a pin or key that extends into central bore410, and that the key help secure the cartridge to a bracket in the saw.

FIGS. 65 through 68 show various views of a cartridge 301 mounted on afirst bracket plate 500, which, in turn, is associated with a secondbracket plate 501. The bracket plates are shown isolated in FIGS. 73through 75. Bracket plates 500 and 501 are mounted on pin 503 adjacentarbor block 502. The bracket plates are spaced apart by spacer 505.

Cartridge 301 is similar to cartridge 300 described above, except thatcartridge 301 includes a tab 504 that fits around a shaft 506 extendingthrough holes 507 in bracket plates 500 and 501. Cartridge 301 alsoincludes a slightly modified cam bushing 508 shown in FIGS. 69 and 70,and a key 510 that extends through the central bore in the bushing toturn the bushing and secure the cartridge to the two bracket plates. Thekey is shown isolated in FIGS. 71 and 72. Cam bushing 508 is similar tocam bushing 388 described above, except that cam bushing 508 includes aninternal key slot 512. Key 510 includes a ridge 514 that fits in slot512 in the bushing. Slot 512 allows key 510 to be inserted in only oneorientation.

Cartridge 301 is mounted in the saw on brackets 500 and 501 by insertingkey 510 through cam bushing 508 and through apertures 516 and 518 inbracket plates 500 and 501, respectively. Hole 516 is shaped toaccommodate ridge 514, as shown in FIG. 74. Ridge 514 on key 510includes slots 520 and 522 that are positioned so that when key 510 isinserted all the way into the bushing, the slots will align with thebracket plates. The key can then be turned to lock the cartridge to thebracket plates. FIG. 76, which shows a bottom view of the cartridgeinstalled on bracket plates 500 and 501 with part of the cartridgehousing removed, shows key 510 inserted through cam bushing 508 andbracket plates 500 and 501.

Bracket plates 500 and 501 are connected to arbor 502 by an arbor link524. The arbor link is shown with other components in FIGS. 65 through68, and is shown isolated in FIGS. 77 through 78. Arbor link 524 isconnected to bracket plate 501 by aperture 526 sliding on pin 506, asshown.

Arbor link 524 includes an elongate aperture 528 configured to receiveend 530 of key 510. End 530 is shaped to fit through aperture 528 whenthe key is inserted through the cam bushing and bracket plates. End 530is also tabbed, as shown in FIGS. 71 and 72, so that when the key isturned, the tabs lock the key in place over aperture 528 and prevent thekey from being retracted. The tabs on end 530 include sloped surfaces532 to facilitate turning of the key. The length of the key is chosenand the tabs on end 530 are configured so that when the key is fullyinserted, turning the key pulls the cartridge, bracket plates and arborlink together.

Additionally, when key 510 is turned, ridge 514 causes cam bushing 508to turn, which then causes the switch contactor in the cartridge topress a tactile switch such as switch 380 to indicate the cartridge isin place, as described above.

Cam bushing 508 also includes a tab 540 that is positioned on the outerflange of the bushing and that remains outside the cartridge. Anaperture 542 is positioned in bracket plate 500 so that the cartridgecannot be mounted on the bracket plate unless tab 540 aligns withaperture 542, and tab 540 cannot align with tab 540 unless the cambushing is oriented so that the slide contactor in the cartridge is up,out of engagement with the tactile switch in the cartridge. In thismanner, the cartridge can only be installed if the tactile switch in thecartridge is off. A user then must insert and turn key 510 to both lockthe cartridge in place and press the tactile switch to signal that thecartridge is properly installed. This prevents the saw from being usedwhen the cartridge is not properly installed in the saw. Aperture 542 isshaped to receive tab 540, and to allow tab 540 to turn when key 510turns cam bushing 508.

Arbor link 524 is connected to arbor block 502 by a bolt 550 thatextends through a slot 552 in the arbor link and threads into a hole inthe arbor block, as shown in FIG. 65. When bolt 550 is loose, moving thearbor link will cause the bracket plates and cartridge to move toward oraway from a blade mounted in the saw. In this manner, the position ofthe cartridge relative to the perimeter of the blade can be adjusted toaccount for slight variances in the size of blades. However, thatadjustment is limited by aperture 528 and key 510. Key 510 will notalign with aperture 528 if the arbor link is moved too much, so thecartridge can be installed only if the arbor link is within anacceptable range of positions. When the arbor link and cartridge areproperly positioned relative to the blade, bolt 550 is tightened to holdthe arbor link in place.

Arbor link 524 also includes a slot 554 that is joined to slot 522. Slot524 allows the arbor link and cartridge to move so that any residualpressure from the spring on the brake pawl after the cartridge has firedcan be released. As explained above, when the cartridge fires, the bladecuts into the brake pawl and stops. However, the spring in the cartridgemay not be fully expanded so there may be residual spring force pushingthe pawl onto the blade. That force should be released before the brakepawl can be knocked off the blade and the spent cartridge replaced.

After the cartridge has fired, key 510 would be withdrawn from the cambushing and bracket plates to allow the arbor link to move freely. Bolt550 would be loosened and arbor link 524 would be moved so that bolt 550slides up into slot 554. The cartridge would then move away from theblade, releasing any residual spring force. The brake pawl can then beknocked off the blade and the spent cartridge replaced.

FIGS. 79 through 81 show a plug 600 to which the cartridge connects whenthe cartridge is installed in the saw. Plug 600 includes a female D-subconnector 602 that corresponds to the male D-sub connector in cartridge301. A plastic casing 604 is molded over and around connector 602.Casing 604 includes four posts 606 that are designed to fit intocorresponding holes 608 in bracket plates 500 and 501. Casing 604 ispositioned between bracket plates 500 and 501 and held in place by theposts and holes. The posts are sized so that they are somewhat smallerthan the holes so that the plug may move slightly to align itself withthe corresponding plug on the cartridge. Casing 604 also includes twosockets 610 configured to accept projections 612 on the cartridgehousing. Projections 612 are shown in FIG. 82 projecting out from onehalf of the cartridge housing. Projections 612 align plug 600 with thecorresponding plug on the cartridge as the cartridge is installed in thesaw. Plug 600 also includes three cords 614 which connect to the twoarbor electrodes in the detection subsystem and to ground. Plug 600 alsoincludes a cord 616 that connects to the switch box for the saw.

Cartridge 300 is sized somewhat wider and taller than cartridge 100, asshown in FIGS. 34, 55, 66 and 68, in order to accommodate moreelectronics and a larger printed circuit board. Essentially all of theelectronics for the saw are included on the circuit board in cartridge300, including the electronics for the detection subsystem, the controlsubsystem, blade-to-pawl spacing, the firing circuit, etc. Placing allor substantially all of the electronics in the cartridge provides thesignificant advantage of being able to update the electronics easily bysimply replacing an old cartridge with a new one. For example, thecontrol subsystem in the saw will typically include a microprocessorcontrolled by software, as described in the documents incorporated byreference, and if that microprocessor or software is ever updated, thenthe new microprocessor or software can be implemented in existing sawsby simply installing a new brake cartridge. The electronics in thecartridge will automatically connect to the power source, on/off switchor switches, arbor electrodes, and other such items, when the cartridgeis plugged in. Placing all or substantially all the electronics in thecartridge also minimizes the number of electrical connections and cordsrequired in the saw. It also keeps the detection electronics near theelectrodes to, thereby making the system less susceptible to noise.Placing the electronics together in the cartridge also facilitatesimplementing the electronics as an application specific integratedcircuit because all of the electronics will be located in one place.

INDUSTRIAL APPLICABILITY

The systems, components and brake cartridges disclosed herein areapplicable to power equipment, and specifically to woodworking equipmentsuch as saws.

It is believed that the disclosure set forth above encompasses multipledistinct inventions with independent utility. While each of theseinventions has been disclosed in its preferred form, the specificembodiments thereof as disclosed and illustrated herein are not to beconsidered in a limiting sense as numerous variations are possible. Thesubject matter of the inventions includes all novel and non-obviouscombinations and sub-combinations of the various elements, features,functions and/or properties disclosed herein. No single feature,function, element or property of the disclosed embodiments is essentialto all of the disclosed inventions. Similarly, where the claims recite“a” or “a first” element or the equivalent thereof, such claims shouldbe understood to include incorporation of one or more such elements,neither requiring nor excluding two or more such elements.

It is believed that the following claims particularly point out certaincombinations and sub-combinations that are directed to one of thedisclosed inventions and are novel and non-obvious. Inventions embodiedin other combinations and sub-combinations of features, functions,elements and/or properties may be claimed through amendment of thepresent claims or presentation of new claims in this or a relatedapplication. Such amended or new claims, whether they are directed to adifferent invention or directed to the same invention, whetherdifferent, broader, narrower or equal in scope to the original claims,are also regarded as included within the subject matter of theinventions of the present disclosure.

1. A brake cartridge for use in safety systems for power tools, thecartridge comprising: a housing; a brake pawl associated with thehousing and adapted to pivot relative to the housing; a spring at leastpartially enclosed in the housing and adapted to pivot the brake pawlrelative to the housing when the spring expands; a fuse wire adapted tohold the spring in compression; circuitry enclosed in the housing andadapted to fuse the fuse wire to release the spring; a plug associatedwith the housing and adapted to engage a corresponding plug in the powertool; and means for determining whether the cartridge is properlyinstalled in a power tool.
 2. The brake cartridge of claim 1, where themeans for determining further comprises switch means for indicating thecartridge is properly installed when the switch means is activated, andswitch contactor means for activating the switch means when thecartridge is properly installed in the power tool.
 3. The brakecartridge of claim 2, where the means for determining further comprisesaperture means for receiving a rotatable key, where rotation of the keycauses the switch contactor means to activate the switch means.
 4. Thebrake cartridge of claim 3, where the aperture means is configured toallow the key to rotate only when the cartridge is properly installed inthe power tool.
 5. A brake cartridge for use in safety systems for powertools, where the brake cartridge includes a housing and a brakingcomponent configured to engage a moving part of the power tool uponoccurrence of a predetermined event, and where the brake cartridgefurther includes means for determining whether the cartridge is properlyinstalled in a power tool.
 6. A brake cartridge for use in safetysystems for power tools, where the brake cartridge includes a housingand a braking component configured to engage a moving part of the powertool upon occurrence of a predetermined event, and where the brakecartridge further includes a switch configured so that properinstallation of the cartridge in a power tool triggers the switch. 7.The brake cartridge of claim 6 where the switch is a tactile switch. 8.The brake cartridge of claim 6 further comprising a switch contactor. 9.The brake cartridge of claim 6 where the switch includes a contactbutton and where the brake cartridge further comprises a switchcontactor configured to contact the contact button.
 10. The brakecartridge of claim 9 where the switch contactor is configured to moveinto and out of contact with the contact button.